Unit 26

1. Unit 26 Environmental Problems associated with the use of fossil fuels

3. How air pollutants are formed? • By the incomplete combustion of fuels / petrol • By the burning of impurities in fuels (such as sulphur dioxide from sulphur impurities.)

4. Test for gases in car exhaust • Test for carbon dioxide • Turns lime water milky. • Test for carbon monoxide • Turns citrated blood cherry red. • Test for acidic gases • Turns universal indicator red.

5. Air pollutants from car exhausts • Carbon monoxide – from the incomplete combustion of petrol. • Unburnt hydrocarbons – such as benzene, C6H6, which is carcinogenic / causing cancer. • Carbon particulates (black smokes) – unburnt carbon particles from the incomplete combustion of fuel • Too small to be filtered by the hairs in the nose. • Causing serious lung diseases .

6. Air pollutants from car exhausts • Nitrogen oxides • High temperature in the cylinders of the car engine and electric sparks / lightening (thunderstorm) • Oxidation of nitrogen • N2(g) + O2(g) 2NO(g) • Oxidation of nitrogen oxide by air • 2NO(g) + O2(g)  2NO2(g)

7. Nitrogen oxides • Poisonous gases • Irritate and attack respiratory system • Dissolving in rainwater to form acid rain. • 2NO2(g) + H2O(l) HNO2(aq) + HNO3(aq)

8. Photochemical smog • Nitrogen oxides together with unburnt hydrocarbons produce photochemical smog. • Smog is poisonous.

9. Lead compounds • Tetraethyl lead – added to petrol for improving the burning of petrol • Lead compounds accumulate in our bodies. They have harmful effects on red blood cells and brain cells.

10. Pollutants from industry • From factories, power stations and incinerators • Same as that from car exhausts • With one more air pollutant (from the burning of sulphur impurities) • Sulphur dioxide

11. Sulphur dioxide • From the burning of coal or low grade petroleum • From the waste gas of incinerators as rubbish (waste paper) contains sulphur compounds as impurities. • Irritates the respiratory systems & affects the normal function of lungs • Causes cancer and even death. • SO2(g) + H2O(l) H2SO3(aq)

12. Acid rain • Is rainwater from non-polluted air acidic? • pH 5.6 • Carbon dioxide dissolves in rainwater to form carbonic acid. • CO2(g) + H2O(l) H2CO3(aq) • Sulphur dioxide and nitrogen dioxide dissolve in rainwater to form acid rain.

13. Effect of acid rain • Harm to water lives • Acid rain makes rivers and lakes more acidic. Harmful to water lives and even kills them. • Damage to forests • Forests seriously damaged by acid rain. Trees are stunted. Leaves drop off and the trees die.

14. Effect of acid rain • Damage to metalwork • Speeding up the rate of corrosion of metals • Damage to building materials • Acid rain attacks buildings made up of limestone.

15. Greenhouse effect • Carbon dioxide in the atmosphere acts like glass of a greenhouse. It allows high energy radiation from the sun to penetrate the atmosphere and warms the Earth’s surface. The high energy radiation is re-radiated as infra-red radiation. However, the infra-red radiation is trapped by the atmosphere (carbon dioxide). The Earth is thus warmed up.

16. Greenhouse gases • Carbon dioxide, methane, nitrogen oxides, ozone and chlorofluorocarbons are greenhouse gases.

17. Ways to reduce the greenhouse effect (to reduce carbon dioxide emission) • Plant more trees • Stop burning fossil fuels • Stop cutting down trees.

18. Methods for reducing air pollution • Using unleaded petrol in cars. • For reducing the amount of lead compounds in air.

19. Methods for reducing air pollution • Installing catalytic converter in car exhaust system • It is a honeycomb structure. • Installed in the exhaust system of cars. • On structure, platinum and other transition metal are deposited.

20. Catalytic converters carbon dioxide (CO2) nitrogen (N2) water (H2O) carbon monoxide (CO) nitrogen oxides (NOx) hydrocarbons (HC) stainless steel case honeycomb-shaped support

21. Shortcoming of catalytic converters • Solid lead compounds deposit on the surface of catalyst and block the honeycomb. • Catalytic converters can only be fitted with motor-cars which are run on unleaded petrol.

22. How does catalytic converter work? • Nitrogen oxide reacts with carbon monoxide when they pass over the catalyst. • 2NO(g) + 2CO(g) N2(g) + 2CO2(g) • The carbon monoxide and unburnt hydrocarbons are oxidized in the presence of catalyst to form harmless products. • 2CO(g) + O2(g)  2CO2(g) • 2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O(l)

23. Using scrubbers in power stations • Removing up to 95% of carbon dioxide. • Two methods of scrubbing • Dry scrubbing • Wet scrubbing

24. Dry scrubbing • Powdered limestone (CaCO3) is blown into the combustion chamber where it decomposes. • CaCO3(S) CaO(s) + CO2(g) • The calcium oxide reacts with sulphur dioxide to form calcium sulphite. • CaO(s) + SO2(g)  CaSO3(s) • These products are washed away as a slurry – a mixture of solids and water.

25. d r y s c r u b b i n g w e t s c r u b b i n g f u r n a c e w a t e r + S + O S O C a O 2 2 C a O c o a l C a C O 3 C a S O + S O 3 2 a i r CaSO3 slurry w a s t e s l u r r y Using scrubbers in power stations

26. Wet scrubbing • Sulphur dioxide is removed by the action of calcium oxide and water (I.e., calcium hydroxide solution). • CaO(s) + H2O(l) Ca(OH)2(aq) • Ca(OH)2(aq) + SO2(g)  CaSO3(s)+ H2O(l)

27. By the electrostatic precipitators in industry • Removes 99% of the particulates.

28. Electrostatic precipitators • Dirty gases pass through a strong electric field. • The particles become charged. • The charged particles are then collected on plates of opposite charge.

29. Role of Governemnt • Legislation • Monitoring and investigating • planning

30. Oil splliage • Petroleum is toxic and flammable. • Pollutes beaches and spoils recreation resorts. • Blocks the oxygen supply of water lives. • Clogs the feathers of birds and prevents them from flying abd swimming. • Poisoned sea birds and fishes.

31. Cleaning up oil spillage • Using detergents to emulsify the oil.